Case 128
- Wangpan Shi
- Jun 1
- 1 min read
A 54-year-old female with a 7.5 cm large gastric mass:
The tumor is negative for pan-keratin and mitotically active with necrosis. What's your diagnosis?
A: Poorly differentiated carcinoma
B: Neuroendocrine carcinoma
C: Gastroblastoma
D: Glomus tumor
E: Malignant glomus tumor
F: Leiomyosarcoma
Answer
The correct answer is E. The tumor is positive for SMA, negative for keratin. This is a case of malignant glomus tumor.
Morphology and Histologic Features:
Similar to peripheral soft tissue glomus tumors
Composed of uniform, small, rounded cells with:
Central, dark round nuclei
Moderate eosinophilic to clear cytoplasm
Sharply defined basal lamina surrounding individual cells
Stroma may be:
Focally myxoid or hyalinized
Rare features:
Epithelioid or oncocytic morphology
Epithelioid cells: large polygonal to spindle-shaped, abundant eosinophilic cytoplasm, large irregular nuclei with atypia (senescent/ancient change)
Peripheral small areas of conventional glomus tumor often present
Location-Specific Features:
Gastric glomus tumors:
May show plexiform growth pattern in muscularis propria
Focal nuclear atypia and vascular invasion are common but not prognostically adverse
Hepatic glomus tumors:
Should be distinguished from metastases
Most show typical glomus tumor features
Malignancy Criteria (GI tract):
Criteria not clearly defined due to limited data
Peripheral soft tissue malignancy criteria may be applied:
Deep location and size > 2 cm
Atypical mitotic figures
Moderate to high nuclear grade
≥ 5 mitoses per 10 mm²
Immunohistochemistry Profile:
Positive:
SMA (diffuse, strong)
Caldesmon (>60% cases)
Collagen IV
Laminin (net-like pericellular pattern)
Cytoplasmic SIRT1 expression
Focal synaptophysin (can be a diagnostic pitfall with NETs)
Negative:
Chromogranin
CD56
Desmin
S100
Keratin
CD34
KIT (CD117)
DOG1
Case credit: UCSD Pathology
Author: Wangpan Shi, MD
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